8 ways you have mentioned can really help you earn money but some of it are just very risky and can also lead to losing your money. In gambling, you can earn but everything there is a risk. Easy money also lose that fast. But if you want to earn bitcoin without investing your money, you can work for it. What you have to invest is your time and effort.
There are so many ways to earn bitcoin but it doesnt mean that you will do all of that because some of that have their own risk factor or level. After reading the article, you have to assess if you can do that or not and choose only the way that is applicable to you, for me bounties and trading is the best way to earn bitcoin.